Machine-switching telephone-exchange system.



C. L. GOODRUIVI.

MACHINE SWITCHING TELEPHONE EXCHANGE SYSTEM.

APPLICATION HLED JULY 23. 1915.

Patented Feb. 1, 1916.

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Chr/es Goodrwm QHARLES I. GOODRUM, OF NEW YORK, N. Y., ASSIGNOR, BY MESNE ASSIGNMENTS, TO WESTERN ELECTRIC COMPANY, INCORPORATED, A CORPORATION OF NEW YORK.

' MACHINE-SWITCHING TELEPHONE-EXCHANGE SYSTEM.

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Specification of Letters ratent. I

Patented Feb. 1, EH6.

Application filed July 23, 1915. Serial No. 41,479.

To all whom it may concern:

Be it known that I, CHARLES L. GOODRUM,'

a citizen of the United States, residing at New York, in the county of New York and State of New York, have invented certain new and useful Improvements in Machine- Switching Telephone-Exchange Systems, of which the following is a full, clear, concise, and exact description. p

This invention relates to telephone "ekchange'systems employing machine switching, and more particularly to what are known as two-wire systems.

It is customary in two-wire systems wherein the automatic selector switches are controlled by side or steering switches, to employ two slow relays and an escapement or side switch control magnet. One of these slow relays is energized by impulses from the armature and front contact of the stepping relay to maintain the circuit of the release magnet open; The other is energized by impulses from the armature and back contact of the stepping relay, and at its armature and front contact closes the circuit of the side switch escapeinent magnet. Thus upon the termination of the line circuit interruptions, caused by the sender transmitting the digit of the called number involved in the operation of the selector switch in question, this relay becomes deenergized and opens the circuit of the escapement magnet. The escapement magnet in retracting its armature releases the side switch, which adrances to the neXt position and prepares the necessary circuits for the next selecting operation of the automatic switch. I

It is the object of this invention to provide an efiicient circuit arrangement of this character wherein two relays only are required to control the selector, instead of three as heretofore. This is accomplished by providing a sl0W release escapement magnet for controlling the side switch, and connecting such magnet to a back contact of the stepping relay as such relay is being operated by the sender. Thus, when the sender is restored, this magnet after a slight interval becomes denergized and allows the side switch to advance to the next position.

The invention will be more readily understood when described with reference to the accompanying drawing wherein Figure 1 shows only so much of a telephone exchange system as is necessary for an understanding of the invention, and Fig. 2 1s a detail of the side switch and its control magnet.

The calling line, whose substation is designated A, may be associated in any wellknown manner with the selector Shown, as, for example, by a line finder whose brushes 14c, 19 and cooperating stationary terminals 15, 18 only are shown. When the calling line has been thus extended to the selector which may be the first in the chain involved in extending the calling line, the stepping relay 10 is energized over the following circuit; free pole of the battery, right winding of said relay, conductor 11, side-switch arm 12 and its first contact, conductor 13, finder brush 14, line terminal 15, line conductor 16, sender 24, the telephonic apparatus at substation A, line conductor 17, line terminal 18, finder brush 19, conductor 20, side switch arm 21 and its first contact, conductor 22, left winding of stepping relay 10, to ground. The energization of the stepping relay closes the circuit of'slow-acting relay 23, which at its back contact opens the release circuit of the selector, and at its front contact prepares the circuit of primary stepping magnet 25.

When the calling subscriber operates his sender 24 and interrupts the line circuit in transmitting the particular digit of the '10 to ground. The-magnet 26, which is the escapement magnet of the side-switch, is'in parallel with the stepping magnet 25, and is also energized upon the first retraction of the armature of the stepping relay 10 over the followin circuit: free pole of battery, magnet 26, s1de switch arm 29 and its first contact, conductors 31, 27, armature and a front contact of slow relay 23, conductor 28, armature and back contact of relay 10. to ground. This magnet byattracting its armature disengages lever Z V (Fig. 2) from tooth I of the toothed member on carried by the armature a of the escapement magnet,

and the spring 8 draws it into engagement engagement with tooth III. th

. switch arms 12 and preventing the tery, secondary .30 and 37, test brush b with tooth II. The contact arms thus remain in engagement with the first set of terr'ninals t in the well-known manner. The escapement magnet 26 is slow acting and remains energized during the interruptions of the line circuit caused by sender 24, thus side switch arms a from advancing. However, when the sender 24 restores and maintains the stepping relay 10 energized, the escapement magnet 26 becomes deenergized. The spring 8' thereupon retracts armature a, whereupon the lever Z is disengaged from tooth II and into At this time e arms a are in engagement with the second set of contacts t. The side switch arm 33, upon reaching its second contact, closes the following circuit to step the brushes 6, b, 6 over the terminals 6, t, t in search'of an idle trunk: free pole of batstepping magnet 32, armature and back contact of saidmagnet, eonductor 34, side switch arm 33 and its second contact, conductors 35 and 36, armature and front contact of stepping relay 10 to ground. The escapement magnet 26 is connected to the test brush 6 in the second position of the side switch by way of the following path: free pole of battery, magnet 26, side switch arm 29 and its second contact, conductors An idle trunk is one whose test terminal 25 is grounded. The escapement magnet 26 is constructed and arranged to allow the side switch to' move from position 2 to position 3 upon its energization. Therefore, when the test brush 6 encounters a grounded test terminal t the escapement magnet 26 becomes energized. The armature a (Fig. 2) disengages lever Z from tooth III whereupon spring 8 moves it into contact with tooth IV. he arms a are at this time in contact with the third set of terminals t. The calling line is now eX- tended by side switch arms 12 and 21 to the succeeding group selector or connector, als the'case may be. The engagement of side 21 with their third contacts causes the energization of a relay similar to relay 10 at the succeeding switch, which, upon energizing, immediately re moves ground from test conductor 38, thus rendering the seized switch unselectable to other testing selectors. The subscriber at substation A will now operate his sender 24 to set the succeeding switches to effect connection with the called line. Upon the termination of the conversation and the replacement of the receivers by the parties, a

ground is placed upon test conductor 38..

closing the following circuit to release the selector: free pole of battery, release magnet 39, conductor 40, primary ofi' normal switch, a spring contact PON, conductors 45, 41, side switch arm 42 and its third contact, conductor 37, test brush 6 test terminal t to grounded conductor 38. The release magnet 39 restores the side switch upon the attraction of its armature in the well-known manner.

pon reaching its normal position, the selector switch shaft will open its primary 01f normal contact PON 1n the well-known manner, thus deenergizing release -magnet 39.

If the subscriber abandons the call while the side switch is in either position 1 or 2, the relay 10 is deenergized, resulting in the denergization of slow acting relay 23. This relay, at its armature and back contact, closes the release circuit as follows: free pole of battery, release magnet 39, conductor 40, primary off normal contact PON, conductor 41, side switch arm 42 and either its first or second contact, conductor 43, armature and back contact of slow relay 23, conductor 28, armature and back contact of stepping relay 10 to ground.

What is claimed is:

1. In a machine switching telephone exchange system, the combination with an automatic selector switch, a stepping relay associated therewith, a sender for operating the same, a slow relay controlled at a front contact of said stepping relay, a release circuitcontrolled at a back contact of said slow relay, a stepping magnet, a circuit therefor, controlled by said stepping relay, a steering normally tending to advance the same, of a slow-acting control magnet for said steering switch adapted to release the same uponits deenergization, and a circuit for said magnet controlled at a back contact of said stepping relay.

2. In a machine switching telephone exchange system, the combination with an au-- tomatic selector switch, a stepping relay associated therewith, a sender for operating the same, a slow relay controlled at a front contact of said stepping relay, a release circuit controlled at a back contact of said slow relay, a primary stepping magnet, a circuit therefor controlled at an armature and back contact of said stepping relay, a steering switch adapted in its first position to connect said magnet to the said back contact, of a slow-acting control magnet adapted to release said steering switch upon its denergization, a circuit for said magnet controlled at a back contact of said stepping relay, a secondary magnet and a circuit therefor adapted to be closed by said steering switch in its succeeding position.

In witness whereof, I hereunto subscribe my name this 21st day of July A. D., 1915.

CHARLES L. GOODRUM. 

